Workaround segfault in clang's mangling code that is tickled when
attempting to mangle the declaration:
 std:__ndk1::__find_detail::__find_exactly_one_checked::__matches
in the <tuple> header in the Android NDK.
This codepath is exercised by MozsearchIndexer.cpp (the searchfox
indexer) when indexing on Android. See also
https://bugs.llvm.org/show_bug.cgi?id=40747

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 2dc04f2f3d8..054fc27003d 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -3495,16 +3495,21 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity) {
   //              ::= <expr-primary>
   // <expr-primary> ::= L <type> <value number> E    # integer literal
   //                ::= L <type <value float> E      # floating literal
   //                ::= L <mangled-name> E           # external name
   //                ::= fpT                          # 'this' expression
   QualType ImplicitlyConvertedToType;
 
 recurse:
+  if (!E) {
+    Out << "MOZ_WE_HACKED_AROUND_BUG_1500941";
+    return;
+  }
+
   switch (E->getStmtClass()) {
   case Expr::NoStmtClass:
 #define ABSTRACT_STMT(Type)
 #define EXPR(Type, Base)
 #define STMT(Type, Base) \
   case Expr::Type##Class:
 #include "clang/AST/StmtNodes.inc"
     // fallthrough